Handheld vacuum cleaner

ABSTRACT

A handheld vacuum cleaner includes a dirt separator. The dirt separator includes a chamber having an inlet through which dirt-laden fluid enters and an outlet through which cleansed fluid exits the chamber. A disc located at the outlet rotates about a rotational axis and comprises holes through which the cleansed fluid passes.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a national stage application under 35 USC 371 ofInternational Application No. PCT/GB2018/052144, filed Jul. 27, 2018,which claims the priority of United Kingdom Application No. 1712935.4,filed Aug. 11, 2017, the entire contents of each of which areincorporated herein by reference.

FIELD OF THE DISCLOSURE

The present invention relates to a handheld vacuum cleaner.

BACKGROUND OF THE DISCLOSURE

A handheld vacuum cleaner may comprise a filter or a cyclonic separatoras the primary means for removing dirt. However, both types of separatorhave their disadvantages. For example, the filter often has a poorseparation efficiency, whilst the pressure consumed by a cyclonicseparator can be high.

SUMMARY OF THE DISCLOSURE

According to various aspects, the present invention provides a handheldvacuum cleaner comprising a dirt separator, the dirt separatorcomprising: a chamber having an inlet through which dirt-laden fluidenters the chamber and an outlet through which cleansed fluid exits thechamber; and a disc located at the outlet, the disc being arranged torotate about a rotational axis and comprising holes through which thecleansed fluid passes.

The dirt-laden fluid entering the chamber contacts the rotating disc,which imparts tangential forces to the fluid. As the dirt-laden fluidmoves radially outward, the tangential forces imparted by the discincrease. The fluid is then drawn through the holes in the disc whilstthe dirt, owing to its greater inertia, continues to move outwards andcollects at the bottom of the chamber.

The handheld vacuum cleaner according to various aspects of the presentinvention has advantages over conventional handheld vacuum cleaners thatemploy filters or cyclonic separators as the primary means for removingdirt. For example, the filter typically has a poor separation efficiencyand/or quickly clogs with dirt. With the handheld vacuum cleaneraccording to various aspects of the present invention, the holes in thedisc may be sized so as to achieve a good separation efficiency, whilstrotation of the disc helps ensure that the holes in the disc aregenerally kept clear of dirt. The cyclonic separator of a vacuum cleanertypically comprises two or more stages of separation. The first stageoften comprises a single larger cyclone chamber for removing coarsedirt, and the second stage comprises a number of smaller cyclonechambers for removing fine dirt. As a result, the overall size of thecyclonic separator can be large. A further difficulty with the cyclonicseparator is that it requires high fluid speeds in order to achieve highseparation efficiencies. Additionally, the fluid moving through thecyclonic separator often follows a relatively long path as it travelsfrom the inlet to the outlet. As a result, the pressure drop associatedwith the cyclonic separator can be high. With the handheld vacuumcleaner according to various aspects of the present invention,relatively high separation efficiencies can be achieved in a morecompact manner In particular, the dirt separator may comprise a singlestage having a single chamber. Furthermore, separation occurs primarilyas a result of the angular momentum imparted to the dirt by the rotatingdisc. As a result, relatively high separation efficiencies may beachieved at relatively low fluid speeds. Additionally, the path taken bythe fluid in moving from the inlet to the outlet of the chamber isrelatively short. As a result, the pressure drop across the dirtseparator may be smaller than that across a cyclonic separator havingthe same separation efficiency.

The provision of a rotating disc within a dirt separator of a vacuumcleaner is known. However, there is an existing prejudice that the dirtseparator must include a cyclone chamber to separate the dirt from thefluid. The disc is then used merely as an auxiliary filter to removeresidual dirt from the fluid as it exits the cyclone chamber. As aresult, the overall size of the dirt separator is relatively large andis unsuitable for use in a handheld vacuum cleaner. According to variousaspects, the present invention is predicated on the realisation thateffective separation may be achieved using a rotating disc without theneed for cyclonic flow. As a result, a dirt separator having a sizesuitable for use in a handheld vacuum cleaner may be realised.

The dirt-laden fluid entering the chamber may be directed at the disc.That is to say that the dirt-laden fluid may enter the chamber via theinlet along a flow axis that intersects the disc. As noted above,although the provision of a rotating disc within a dirt separator of avacuum cleaner is known, there is an existing prejudice that the dirtseparator must include a cyclone chamber to separate the dirt from thefluid. There is a further prejudice that the rotating disc must beprotected from the bulk of the dirt that enters the cyclone chamber. Asa result, the dirt-laden fluid is introduced into the cyclone chamber ina manner that avoids direct collision with the disc. However, bydirecting the dirt-laden fluid at the disc, the dirt is subjected torelatively high tangential forces upon contact with the rotating disc.Dirt within the fluid is then thrown radially outward whilst the fluidpasses axially through the holes in the disc. As a result, effectivedirt separation may be achieved without the need for cyclonic flow.

The dirt-laden fluid entering the chamber may be directed at the centreof the disc. That is to say that the flow axis may intersect the centreof the disc. This then has the advantage that the flow of the dirt-ladenfluid over the surface of the disc may be more evenly distributed. Bycontrast, if the dirt-laden fluid were directed off-centre at the disc,the fluid would most likely be unevenly distributed. The axial speed ofthe fluid moving through the holes may then increase at those regions ofthe disc that are most heavily loaded, resulting in a decrease inseparation efficiency. Additionally, dirt separated from the fluid maycollect unevenly within the chamber, thereby compromising the capacityof the dirt separator. Re-entrainment of dirt may also increase, leadingto a further decrease in the separation efficiency. A furtherdisadvantage of directing the dirt-laden fluid off-centre is that thedisc may be subjected to uneven structural load. The resulting imbalancemay lead to increased vibration and noise, and/or may reduce thelifespan of any bearings used to support the rotating disc.

Dirt separated from the dirt-laden fluid may collect at a bottom of thechamber and fill progressively in a direction towards a top of thechamber. The outlet may then be located at or adjacent the top of thechamber, and the bottom of the chamber may be spaced axially from thetop of the chamber. By locating the outlet at or adjacent the top of thechamber, the disc may be kept clear of the separated dirt that collectswithin the chamber. As a result, effective separation may be maintainedas the chamber fills with dirt. The bottom of the chamber is spacedaxially (i.e. in a direction parallel the rotational axis) from the topof the chamber. This then has the benefit that dirt and fluid thrownradially outward by the disc is less likely to disturb the dirtcollected at the bottom of the chamber. Additionally, any swirl withinthe chamber is likely to move around the chamber rather than up and downthe chamber. As a result, re-entrainment of dirt collected in thechamber may be reduced, resulting in improved separation efficiency.

In contrast to an upright or canister vacuum cleaner, the orientation ofa handheld vacuum cleaner often changes as the vacuum cleaner is used toclean different surfaces. For example, the vacuum cleaner may bedirected downwards when cleaning floors, but upwards when cleaningceilings. When switching between the two orientations, dirt alreadycollected in the chamber may fall onto the disc. This may damage thedisc or reduce the separation efficiency of the dirt separator. Thechamber may therefore extend above and below the disc in a directionparallel to the rotational axis. Dirt separated from the dirt-ladenfluid then collects in a lower portion of the chamber located below thedisc when the vacuum cleaner is used in a first orientation (e.g. toclean floors), and dirt collected in the lower portion moves to an upperportion of the chamber located above the disc when the vacuum cleaner isused in a second orientation (e.g. to clean ceilings). As a result, thedisc is better protected from dirt moving down the chamber when theorientation of the vacuum cleaner changes.

The inlet may be defined by an end of an inlet duct and the chamber maysurround the inlet duct. That is to say that the chamber may surroundthe inlet duct along the full length of the inlet duct extending withinthe chamber. As a result, dirt is less likely to become trapped betweenthe inlet duct and a surrounding wall of the chamber.

The inlet may defined by an end of an inlet duct that extends through awall of the chamber, and an opposite end of the inlet duct may beattachable to different attachments of the vacuum cleaner. Inparticular, the inlet duct may be attachable to different accessorytools of the vacuum cleaner. By providing an inlet duct to whichdifferent attachments may be directly attached, a relatively short pathmay be provided between the different attachments and the dirtseparator. As a result, pressure losses may be reduced.

The inlet may be defined by an end of an inlet duct that extendslinearly within the chamber. This then has the advantage that thedirt-laden fluid moves through the inlet duct along a straight path andthus pressure losses may be reduced.

The inlet may be defined by an end of an inlet duct, a wall of thechamber may be moveable between an open position and a closed position,and the inlet duct may be attached to and moveable with the wall. Havinga wall that moves between open and closed positions simplifies emptyingof the dirt separator. Having an inlet duct that is attached to and ismoveable with the wall helps encourage the removal of dirt when the wallmoves to the open position. For example, when the wall moves to the openposition, the moving inlet duct may push or pull dirt out of thechamber. Moreover, if the inlet duct were to remain within the chamberwhen the wall moves to the open position, dirt may be retained betweenthe inlet duct and a surrounding wall of the chamber.

The disc may be formed of metal. This has at least two benefits over,say, a disc formed of plastic. First, a relatively thin disc having arelatively high stiffness may be achieved. Second, the disc is lesssusceptible to damage from hard or sharp objects carried by the fluid.This is of particular importance since the dirt-laden fluid entering thechamber is directed at the disc.

According to various aspects, the present invention also provides astick vacuum cleaner comprising a handheld vacuum cleaner as describedin any one of the preceding paragraphs attached to a cleaner head by anelongate tube, the elongate tube extending along an axis parallel to therotational axis.

By having an elongate tube that extends parallel to the rotational axis,dirt-laden fluid may be carried from the cleaner head to the dirtseparator and the rotating disc along a relatively straight path. As aresult, pressure losses may be reduced.

The dirt separator may comprise an inlet duct that extends through awall of the chamber, the inlet is defined by a first end of the inletduct, and the elongate tube is attached to a second end of the inletduct. By providing an inlet duct to which the elongate tube is directlyattached, a relatively short path may be provided between the cleanerhead and the dirt separator. As a result, pressure losses may bereduced.

BRIEF DESCRIPTION OF THE FIGURES

In order that the present invention may be more readily understood,embodiments of the invention will now be described, by way of example,with reference to the accompanying drawings in which:

FIG. 1 is a perspective view of a vacuum cleaner;

FIG. 2 is a section through a part of the vacuum cleaner;

FIG. 3 is a section through a dirt separator of the vacuum cleaner;

FIG. 4 is a plan view of a disc of the dirt separator;

FIG. 5 illustrates the flow of dirt-laden fluid through the dirtseparator;

FIG. 6 illustrates emptying of the dirt separator;

FIG. 7 is a section through a part of the vacuum cleaner when used forabove-floor cleaning;

FIG. 8 illustrates the tangential forces imparted by the disc to thedirt-laden fluid at the circumference of an inlet duct that is (a)directed at the centre of the disc and (b) is directed off-centre;

FIG. 9 is a section through a first alternative dirt separator;

FIG. 10 is a section through a part of a vacuum cleaner having a secondalternative dirt separator;

FIG. 11 is a section through a third alternative dirt separator;

FIG. 12 is a section through a part of a vacuum cleaner having the thirdalternative dirt separator;

FIG. 13 illustrates emptying of the third alternative dirt separator;

FIG. 14 is a section through a fourth alternative dirt separator; and

FIG. 15 illustrates an alternative disc assembly that may form part ofany one of the dirt separators.

DETAILED DESCRIPTION OF THE DISCLOSURE

The vacuum cleaner 1 of FIG. 1 comprises a handheld unit 2 attached to acleaner head 4 by means of an elongate tube 3. The elongate tube 3 isdetachable from the handheld unit 2 such that the handheld unit 2 may beused as a standalone vacuum cleaner.

Referring now to FIGS. 2 to 7, the handheld unit 2 comprises a dirtseparator 10, a pre-motor filter 11, a vacuum motor 12 and a post-motorfilter 13. The pre-motor filter 11 is located downstream of the dirtseparator 10 but upstream of the vacuum motor 12, and the post-motorfilter 13 is located downstream of the vacuum motor 12. During use, thevacuum motor 12 causes dirt-laden fluid to be drawn in through a suctionopening in the underside of the cleaner head 4. From the cleaner head 4,the dirt-laden fluid is drawn along the elongate tube 3 and into thedirt separator 10. Dirt is then separated from the fluid and retainedwithin the dirt separator 10. The cleansed fluid exits the dirtseparator 10 and is drawn through the pre-motor filter 11, which removesresidual dirt from the fluid before passing through the vacuum motor 12.Finally, the fluid expelled by the vacuum motor 12 passes through thepost-motor filter 13 and is exhausted from the vacuum cleaner 1 viavents 14 in the handheld unit 2.

The dirt separator comprises a container 20, an inlet duct 21, and adisc assembly 22.

The container 20 comprises a top wall 30, a side wall 31, and a bottomwall 32 that collectively define a chamber 36. An opening in the centreof the top wall defines an outlet 38 of the chamber 36. The bottom wall32 is attached to the side wall 31 by means of a hinge 33. A catch 34attached to the bottom wall 32 engages with a recess in the side wall 31to hold the bottom wall 32 in a closed position. Releasing the catch 34then causes the bottom wall 32 to swing to an open position, asillustrated in FIG. 6.

The inlet duct 21 extends upwardly through the bottom wall 32 of thecontainer 20. The inlet duct 21 extends centrally within the chamber 36and terminates a short distance from the disc assembly 22. One end ofthe inlet duct 21 defines an inlet 37 of the chamber 36. The oppositeend of the inlet duct 21 is attachable to the elongate tube 3 or anaccessory tool when the handheld unit 2 is used as a standalone cleaner.

The disc assembly 22 comprises a disc 40 coupled to an electric motor41. The electric motor 41 is located outside of the chamber 36, and thedisc 40 is located at and covers the outlet 38 of the chamber 36. Whenpowered on, the electric motor 41 causes the disc 40 to rotate about arotational axis 48. The disc 40 is formed of a metal and comprises acentral non-perforated region 45 surrounded by a perforated region 46.The periphery of the disc 40 overlies the top wall 30 of the container20. As the disc 40 rotates, the periphery of the disc 40 contacts andforms a seal with the top wall 30. In order to reduce friction betweenthe disc 40 and the top wall 30, a ring of low-friction material (e.g.PTFE) may be provided around the top wall 30.

During use, the vacuum motor 12 causes dirt-laden fluid to be drawn intothe chamber 36 via the inlet 37. The inlet duct 21 extends centrallywithin the chamber 36 along an axis that is coincident with therotational axis 48 of the disc 40. As a result, the dirt-laden fluidenters the chamber 36 in an axial direction (i.e. in a directionparallel to the rotational axis 48). Moreover, the dirt-laden fluid isdirected at the centre of the disc 40. The central non-perforated regionof the disc 40 causes the dirt-laden fluid to turn and move radiallyoutward (i.e. in a direction normal to the rotational axis). Therotating disc 40 imparts tangential forces to the dirt-laden fluid,causing the fluid to swirl. As the dirt-laden fluid moves radiallyoutward, the tangential forces imparted by the disc 40 increase. Uponreaching the perforated region 46 of the disc 40, the fluid is drawnaxially through the holes 47 in the disc 40. This requires a furtherturn in the direction of the fluid. The inertia of the larger andheavier dirt is too great to allow the dirt to follow the fluid. As aresult, rather than being drawn through the holes 47, the dirt continuesto move radially outwards and eventually collects at the bottom of thechamber 36. Smaller and lighter dirt may follow the fluid through thedisc 40. The bulk of this dirt is then subsequently removed by thepre-motor and post-motor filters 11, 13. In order to empty the dirtseparator 10, the catch 34 is released and the bottom wall 32 of thecontainer 20 swings open. As illustrated in FIG. 6, the container 20 andthe inlet duct 21 are configured such that the inlet duct 21 does notprevent or otherwise hinder the movement of the bottom wall 32.

In addition to cleaning floor surfaces, the vacuum cleaner 1 may be usedto clean above-floor surfaces such as shelves, curtains or ceilings.When cleaning these surfaces, the handheld unit 2 may be inverted asshown in FIG. 7. Dirt 50 collected in the chamber 36 may then fall downtowards the disc 40. Any dirt falling onto the disc 40 is likely to bedrawn through or block some of the holes 47 in the perforated region 46.As a result, the available open area of the disc 40 will decrease andthe speed of the fluid moving axially through the disc 40 will increase.More dirt is then likely to be carried by the fluid through the disc 40and thus the separation efficiency of the dirt separator 10 is likely todecrease. The top wall 30 of the container 20 is not flat but is insteadstepped. As a result, the chamber 36 comprises a gulley located betweenthe side wall 31 and the step in the top wall 30. This gulley surroundsthe disc 40 and acts to collect dirt 50 that falls down the chamber 36.As a result, less dirt is likely to fall onto the disc 40 when thehandheld unit 2 is inverted.

The dirt separator 10 has several advantages over a conventionalseparator that employs a porous bag. The pores of a bag quickly clogwith dirt during use. This then reduces the suction that is achieved atthe cleaner head. Additionally, the bag must normally be replaced whenfull, and it is not always easy to determine when the bag is full. Withthe dirt separator described herein, rotation of the disc 40 ensuresthat the holes 47 in the perforated region 46 are generally kept clearof dirt. As a result, no significant reduction in suction is observedduring use. Additionally, the dirt separator 10 may be emptied byopening the bottom wall 32 of the container 20, thus avoiding the needfor replacement bags. Furthermore, by employing a transparent materialfor the side wall 31 of the container 20, a user is able to determinewith relative ease when the dirt separator 10 is full and requiresemptying. The aforementioned disadvantages of a porous bag are wellknown and are solved equally well by a separator that employs cyclonicseparation. However, the dirt separator 10 described herein also hasadvantages over a cyclonic separator.

In order to achieve a relatively high separation efficiency, thecyclonic separator of a vacuum cleaner typically comprises two or morestages of separation. The first stage often comprises a single,relatively large cyclone chamber for removing coarse dirt, and thesecond stage comprises a number of relatively small cyclone chambers forremoving fine dirt. As a result, the overall size of the cyclonicseparator can be relatively large. A further difficulty with thecyclonic separator is that it requires high fluid speeds in order toachieve high separation efficiencies. Furthermore, the fluid movingthrough the cyclonic separator often follows a relatively long path asit travels from the inlet to the outlet. The long path and high speedsresult in high aerodynamic losses. As a result, the pressure dropassociated with the cyclonic separator can be high. With the dirtseparator described herein, relatively high separation efficiencies canbe achieved in a more compact manner In particular, the dirt separatorcomprises a single stage having a single chamber. Furthermore,separation occurs primarily as a result of the angular momentum impartedto the dirt-laden fluid by the rotating disc 40. As a result, relativelyhigh separation efficiencies can be achieved at relatively low fluidspeeds. Additionally, the path taken by the fluid in moving from theinlet 37 to the outlet 38 of the dirt separator 10 is comparativelyshort. As a consequence of the lower fluid speeds and shorter path,aerodynamic losses are smaller. As a result, the pressure drop acrossthe dirt separator 10 is smaller than that across the cyclonicseparator, for the same separation efficiency. The vacuum cleaner 1 istherefore able to achieve the same cleaning performance as that of acyclonic vacuum cleaner using a less powerful vacuum motor. This isparticularly important should the vacuum cleaner 1 be powered by abattery, since any reduction in the power consumption of the vacuummotor 11 may be used to increase the runtime of the vacuum cleaner 1.

The provision of a rotating disc within a dirt separator of a vacuumcleaner is known. For example, DE19637431 and U.S. Pat. No. 4,382,804each describe a dirt separator having a rotating disc. However, there isan existing prejudice that the dirt separator must include a cyclonechamber to separate the dirt from the fluid. The disc is then usedmerely as an auxiliary filter to remove residual dirt from the fluid asit exits the cyclone chamber. There is a further prejudice that therotating disc must be protected from the bulk of the dirt that entersthe cyclone chamber. The dirt-laden fluid is therefore introduced intothe cyclone chamber in a manner that avoids direct collision with thedisc.

The dirt separator described herein exploits the finding that dirtseparation may be achieved with a rotating disc without the need for acyclone chamber. The dirt separator further exploits the finding thateffective dirt separation may be achieved by introducing the dirt-ladenfluid into a chamber in a direction directly towards the disc. Bydirecting the dirt-laden fluid at the disc, the dirt is subjected torelatively high forces upon contact with the rotating disc. Dirt withinthe fluid is then thrown radially outward whilst the fluid passesaxially through the holes in the disc. As a result, effective dirtseparation is achieved without the need for cyclonic flow.

The separation efficiency of the dirt separator 10 and the pressure dropacross the dirt separator 10 are sensitive to the size of the holes 47in the disc 40. For a given total open area, the separation efficiencyof the dirt separator 10 increases as the hole size decreases. However,the pressure drop across the dirt separator 10 also increases as thehole size decreases. The separation efficiency and the pressure drop arealso sensitive to the total open area of the disc 40. In particular, asthe total open area increases, the axial speed of the fluid movingthrough the disc 40 decreases. As a result, the separation efficiencyincreases and the pressure drop decreases. It is therefore advantageousto have a large total open area. However, increasing the total open areaof the disc 40 is not without its difficulties. For example, as alreadynoted, increasing the size of the holes in order to increase the totalopen area may actually decrease the separation efficiency. As analternative, the total open area may be increased by increasing the sizeof the perforated region 46. This may be achieved by increasing the sizeof the disc 40 or by decreasing the size of the non-perforated region45. However, each of these options has its disadvantages. For example,since a contact seal is formed between the periphery of the disc 40 andthe top wall 30, more power will be required to drive a disc 40 having alarger diameter. Additionally, a rotating disc 40 of larger diameter maygenerate more stirring within the chamber 36. As a result,re-entrainment of dirt already collected in the chamber 36 may increaseand thus there may actually be a net decrease in the separationefficiency. On the other hand, if the diameter of the non-perforatedregion 45 were decreased then, for reasons detailed below, the axialspeed of the fluid moving through the disc 40 may actually increase.Another way of increasing the total open area of the disc 40 is todecrease the land between the holes 47. However, decreasing the land hasits own difficulties. For example, the stiffness of the disc 40 islikely to decrease and the perforated region 46 is likely to become morefragile and thus more susceptible to damage. Additionally, decreasingthe land between holes may introduce manufacturing difficulties. Thereare therefore many factors to consider in the design of the disc 40.

The disc 40 comprises a central non-perforated region 45 surrounded by aperforated region 46. The provision of a central non-perforated region45 has several advantages, which will now be described.

The stiffness of the disc 40 may be important in achieving an effectivecontact seal between the disc 40 and the top wall 30 of the container20. Having a central region 45 that is non-perforated increases thestiffness of the disc 40. As a result, a thinner disc may be employed.This then has the benefit that the disc 40 may be manufactured in a moretimely and cost-effective manner Moreover, for certain methods ofmanufacture (e.g. chemical etching), the thickness of the disc 40 maydefine the minimum possible dimensions for the holes 47 and land. Athinner disc therefore has the benefit that such methods may be used tomanufacture a disc having relatively small hole and/or land dimensions.Furthermore, the cost and/or weight of the disc 40, along with themechanical power required to drive the disc 40, may be reduced.Consequently, a less powerful, and potentially smaller and cheaper motor41 may be used to drive the disc 40.

By having a central non-perforated region 45, the dirt-laden fluidentering the chamber 36 is forced to turn from an axial direction to aradial direction. The dirt-laden fluid then moves outward over thesurface of the disc 40. This then has at least two benefits. First, asthe dirt-laden fluid moves over the perforated region 46, the fluid isrequired to turn through a relatively large angle (around 90 degrees) inorder to pass through the holes 47 in the disc 40. As a result, less ofthe dirt carried by the fluid is able to match the turn and pass throughthe holes 47. Second, as the dirt-laden fluid moves outward over thesurface of the disc 40, the dirt-laden fluid helps to scrub theperforated region 46. Consequently, any dirt that may have becometrapped at a hole 47 is swept clear by the fluid.

The tangential speed of the disc 40 decreases from the perimeter to thecentre of the disc 40. As a result, the tangential forces imparted tothe dirt-laden fluid by the disc 40 decrease from the perimeter to thecentre. If the central region 45 of the disc 40 were perforated, moredirt is likely to pass through the disc 40. By having a centralnon-perforated region 45, the holes 47 are provided at regions of thedisc 40 where the tangential speeds and thus the tangential forcesimparted to the dirt are relatively high.

As the dirt-laden fluid introduced into the chamber 36 turns from axialto radial, relatively heavy dirt may continue to travel in an axialdirection and impact the disc 40. If the central region 45 of the disc40 were perforated, relatively hard objects impacting the disc 40 maypuncture or otherwise damage the land between the holes 47. By having acentral region 45 that is non-perforated, the risk of damaging the disc40 is reduced.

The diameter of the non-perforated region 45 is greater than thediameter of the inlet 37. As a result, hard objects carried by the fluidare less likely to impact the perforated region 46 and damage the disc40. Additionally, the dirt-laden fluid is better encouraged to turn froman axial direction to a radial direction on entering the chamber 36. Theseparation distance between the inlet 37 and the disc 40 plays animportant part in achieving both these benefits. As the separationdistance between the inlet 37 and the disc 40 increases, the radialcomponent of the velocity of the dirt-laden fluid at the perforatedregion 46 of the disc 40 is likely to decrease. As a result, more dirtis likely to be carried through the holes 47 in the disc 40.Additionally, as the separation distance increases, hard objects carriedby the fluid are more likely to impact the perforated region 46 anddamage the disc 40. A relatively small separation distance is thereforedesirable. However, if the separation distance is too small, dirt largerthan the separation distance will be unable to pass between the inletduct 21 and the disc 40 and will therefore become trapped. The size ofthe dirt carried by the fluid will be limited by, among other things,the diameter of the inlet duct 21. In particular, the size of the dirtis unlikely to be greater than the diameter of the inlet duct 21.Accordingly, by employing a separation distance that is no greater thanthe diameter of the inlet 37, the aforementioned benefits may beachieved whilst providing sufficient space for dirt to pass between theinlet duct 21 and the disc 40.

Irrespective of the separation distance that is chosen, thenon-perforated region 45 of the disc 40 continues to provide advantages.In particular, the non-perforated region 45 ensures that the holes 47 inthe disc 40 are provided at regions where tangential forces imparted tothe dirt by the disc 40 are relatively high. Additionally, although thedirt-laden fluid follows a more divergent path as the separationdistance increases, relatively heavy objects are still likely tocontinue along a relatively straight path upon entering the chamber 36.A central non-perforated region 45 therefore continues to protect thedisc 40 from potential damage.

In spite of the advantages, the diameter of the non-perforated region 45need not be greater than the diameter of the inlet 37. By decreasing thesize of the non-perforated region 45, the size of the perforated region46 and thus the total open area of the disc 46 may be increased. As aresult, the pressure drop across the dirt separator 10 is likely todecrease. Additionally, a decrease in the axial speed of the dirt-ladenfluid moving through the perforated region 46 may be observed. However,as the size of the non-perforated region 45 decreases, there will come apoint at which the fluid entering the chamber 36 is no longer forced toturn from axial to radial before encountering the perforated region 46.There will therefore come a point at which the decrease in axial speeddue to the larger open area is offset by the increase in axial speed dueto the smaller turn angle.

Conceivably, the central region 45 of the disc 40 may be perforated.Although many of the advantages described above would then be forfeited,there may nevertheless be advantages in having a disc 40 that is fullyperforated. For example, it may be simpler and/or cheaper to manufacturethe disc 40. In particular, the disc 40 may be cut from a continuouslyperforated sheet. Even if the central region 45 were perforated, thedisc 40 would continue to impart tangential forces to the dirt-ladenfluid entering the chamber 36, albeit smaller forces at the centre ofthe disc 40. The disc 40 would therefore continue to separate dirt fromthe fluid, albeit at a reduced separation efficiency. Additionally, ifthe central region 45 of the disc 40 were perforated, dirt may block theholes at the very centre of the disc 40 owing to the relatively lowtangential forces imparted by the disc 40. With the holes at the verycentre blocked, the disc 40 would then behave as if the centre of thedisc 40 were non-perforated. Alternatively, the central region 45 may beperforated but have an open area that is less than that of thesurrounding perforated region 46. Moreover, the open area of the centralregion 45 may increase as one moves radially outward from the centre ofthe disc 40. This then has the benefit that the open area of the centralregion 45 increases as the tangential speed of the disc 40 increases.

The inlet duct 21 extends along an axis that is coincident with therotational axis 48 of the disc 40. As a result, the dirt-laden fluidentering the chamber 36 is directed at the centre of the disc 40. Thisthen has the advantage that the dirt-laden fluid is distributed evenlyover the surface of the disc 40. By contrast, if the inlet duct 21 weredirected off-centre at the disc 40, the fluid would be unevenlydistributed. In order to illustrate this point, FIG. 8 shows thetangential forces imparted to the dirt-laden fluid by the disc at thecircumference of an inlet duct 21 that is (a) directed at the centre ofthe disc 40 and (b) is directed off-centre. It can be seen that, whenthe inlet duct 21 is directed off-centre, the dirt-laden fluid does notflow evenly over the surface of the disc 40. In the example shown inFIG. 8(b), the lower half of the disc 40 sees very little of thedirt-laden fluid. This uneven distribution of fluid over the disc 40 islikely to have one or more adverse effects. For example, the axial speedof the fluid through the disc 40 is likely to increase at those regionsthat are most heavily exposed to the dirt-laden fluid. As a result, theseparation efficiency of the dirt separator 10 is likely to decrease.Additionally, dirt separated by the disc 40 may collect unevenly withinthe container 20. As a result, the capacity of the dirt separator 10 maybe compromised. Re-entrainment of dirt 50 already collected within thecontainer 20 may also increase, leading to a further decrease in theseparation efficiency. A further disadvantage of directing thedirt-laden fluid off-centre is that the disc 40 is subjected to unevenstructural load. The resulting imbalance may lead to a poor seal withthe top wall 30 of the container 20, and may reduce the lifespan of anybearings used to support the disc assembly 22 within the vacuum cleaner1.

The inlet duct 21 is attached to and may be formed integrally with thebottom wall 32. The inlet duct 21 is therefore supported within thechamber by the bottom wall 32. The inlet duct 21 may alternatively besupported by the side wall 31 of the container 20, e.g. using one ormore braces that extend radially between the inlet duct 21 and the sidewall 31. This arrangement has the advantage that the bottom wall 32 isfree to open and close without movement of the inlet duct 21. As aresult, a taller container 20 having a larger dirt capacity may beemployed. However, a disadvantage with this arrangement is that thebraces used to support the inlet duct 21 are likely to inhibit dirtfalling from the chamber 36 when the bottom wall 32 is opened, thusmaking emptying of the container 20 more difficult.

The inlet duct 21 extends linearly within the chamber 36. This then hasthe advantage that the dirt-laden fluid moves through the inlet duct 21along a straight path. However, this arrangement is not without itsdifficulties. The bottom wall 32 is arranged to open and close and isattached to the side wall 31 by means of a hinge 33 and catch 34.Accordingly, when a user applies a force to the handheld unit 2 in orderto manoeuvre the cleaner head 4 (e.g. a push or pull force in order tomanoeuvre the cleaner head 4 forwards and backwards, a twisting force inorder to steer the cleaner head 4 left or right, or a lifting force inorder to lift the cleaner head 4 off the floor), the force istransferred to the cleaner head 4 via the hinge 33 and catch 34. Thehinge 33 and catch 34 must therefore be designed in order to withstandthe required forces. As an alternative arrangement, the bottom wall 32may be fixed to the side wall 31, and the side wall 31 may be removablyattached to the top wall 30. The container 20 is then emptied byremoving the side and bottom walls 31, 32 from the top wall 30 andinverting. Although this arrangement has the advantage that it is notnecessary to design a hinge and catch capable of withstanding therequired forces, the dirt separator 10 is less convenient to empty.

An alternative dirt separator 101 is illustrated in FIG. 9. Part of theinlet duct 21 extends along and is attached to or is formed integrallywith the side wall 31 of the container 20. The bottom wall 32 is againattached to the side wall 31 by a hinge 33 and catch (not shown).However, the inlet duct 21 no longer extends through the bottom wall 32.Accordingly, when the bottom wall 32 moves between the closed and openedpositions, the position of the inlet duct 21 is unchanged. This then hasthe advantage that the container 20 is convenient to empty without theneed to design a hinge and catch capable of withstanding the requiredforces. However, as is evident from FIG. 9, the inlet duct 21 is nolonger straight. As a result, there will be increased losses due to thebends in the inlet duct 21 and thus the pressure drop associated withthe dirt separator 10 is likely to increase. Although the inlet duct 21of the arrangement shown in FIG. 9 is no longer straight, the endportion of the inlet duct 21 continues to extend along an axis that iscoincident with the rotational axis 48 of the disc 40. As a result, thedirt-laden fluid continues to enter the chamber 36 in an axial directionthat is directed at the centre of the disc 40.

FIG. 10 illustrates a further dirt separator 102 in which the inlet duct21 extends linearly through the side wall 31 of the container 20. Thebottom wall 32 is then attached to the side wall 31 by means of a hinge33 and is held closed by a catch 34. In the arrangements illustrated inFIGS. 3 and 9, the chamber 36 of the dirt separator 10, 101 isessentially cylindrical in shape, with the longitudinal axis of thechamber 36 coincident with the rotational axis 48 of the disc. The disc40 is then located towards the top of the chamber 36, and the inlet duct21 extends upwardly from the bottom of the chamber 36. Reference to topand bottom should be understood to mean that dirt separated from thefluid collects preferentially at the bottom of the chamber 36, and fillsprogressively in a direction towards the top of the chamber 36. With thearrangement shown in FIG. 10, the shape of the chamber 36 may be thoughtof as the union of a cylindrical top portion and a cubical bottomportion. Both the disc 40 and the inlet duct 21 are then located towardsthe top of the chamber 36. Since the inlet duct 21 extends through theside wall 31 of the container 20, this arrangement has the advantagethat the container 20 may be conveniently emptied via the bottom wall 32without the need for a hinge and catch capable of withstanding theforces required to manoeuvre the cleaner head 4. Additionally, since theinlet duct 21 is linear, pressure losses associated with the inlet duct21 are reduced. The arrangement has at least three further advantages.First, the dirt capacity of the dirt separator 102 is significantlyincreased. Second, when the handheld unit 2 is inverted for above-floorcleaning, dirt within the container 20 is less likely to fall onto thedisc 40. There is therefore no need for the chamber 36 to include aprotective gulley around the disc 40, and thus a larger disc 40 having alarger total open area may be used. Third, the bottom wall 32 of thecontainer 20 may be used to support the handheld unit 2 when resting ona level surface. This arrangement is not, however, without itsdisadvantages. For example, the larger container 20 may obstruct accessto narrow spaces, such as between items of furniture or appliances.Additionally, the bottom of the chamber 36 is spaced radially from thetop of the chamber 36. That is to say that the bottom of the chamber 36is spaced from the top of the chamber 36 in a direction normal to therotational axis 48 of the disc 40. As a result, dirt and fluid thrownradially outward by the disc 40 may disturb the dirt collected in thebottom of the chamber 36. Additionally, any swirl within the chamber 36will tend to move up and down the chamber 36. Consequently,re-entrainment of dirt may increase, resulting in a decrease inseparation efficiency. By contrast, in the arrangements illustrated inFIGS. 3 and 9, the bottom of the chamber 36 is spaced axially from thetop of the chamber 36. Dirt and fluid thrown radially outward by thedisc 40 is therefore less likely to disturb the dirt collected in thebottom of the chamber 36. Additionally, any swirl within the chamber 36moves around the chamber 36 rather than up and down the chamber 36.

In each of the dirt separators 10, 101, 102 described above, at leastthe end portion of the inlet duct 21 (i.e. that portion having the inlet37) extends along an axis that is coincident with the rotational axis 48of the disc 40. As a result, the dirt-laden fluid enters the chamber 36in an axial direction that is directed at the centre of the disc 40. Theadvantages of this have been described above. However, there mayinstances for which it is desirable to have an alternative arrangement.For example, FIGS. 11-13 illustrate a dirt separator 103 in which theinlet duct 21 extends along an axis that is angled relative to therotational axis 48 of the disc 40. That is to say that the inlet duct 21extends along an axis that is non-parallel to the rotational axis 48. Asa consequence of this arrangement, the dirt-laden fluid enters thechamber in a direction that is non-parallel to the rotational axis 48.Nevertheless, the dirt-laden fluid entering the chamber 36 continues tobe directed at the disc 40. Indeed, with the dirt separator 103 shown inFIGS. 11-13, the dirt-laden fluid continues to be directed at the centreof the disc 40. This particular arrangement may be advantageous for acouple of reasons. First, when the vacuum cleaner 1 is used for floorcleaning, as shown in FIG. 1, the handheld unit 2 is generally directeddownwards at an angle of about 45 degrees. As a result, dirt may collectunevenly within the dirt separator. In particular, dirt may collectpreferentially along one side of the chamber 36. With the dirt separator10 shown in FIG. 3, this uneven collection of dirt may mean that dirtfills to the top of the chamber 36 along one side, thus triggering achamber-full condition, even though the opposite side of the chamber 36may be relatively free of dirt. As illustrated in FIG. 12, the dirtseparator 103 of FIGS. 11-13 may make better use of the available space.As a result, the capacity of the dirt separator 10 may be improved. Thedirt separator 101 of FIG. 9 may also be said to have this advantage.However, the inlet duct 21 of the dirt separator 101 includes two bends.By contrast, the inlet duct 21 of the dirt separator 103 of FIGS. 11-13is generally linear, and thus pressure losses are smaller. A furtheradvantage of the arrangement shown in FIGS. 11-13 relates to emptying.As with the arrangement shown in FIG. 3, the inlet duct 21 is attachedto and is moveable with the bottom wall 32. As shown in FIG. 6, when thedirt separator 10 of FIG. 3 is held vertically and the bottom wall 32 isin the open position, the inlet duct 21 extends horizontally. Bycontrast, as shown in FIG. 13, when the dirt separator 103 of FIGS.11-13 is held vertically and the bottom wall 32 is opened, the inletduct 21 is inclined downward. As a result, dirt is better encouraged toslide off the inlet duct 21.

In the arrangement shown in FIGS. 11-13, the dirt-laden fluid enteringthe chamber 36 continues to be directed at the centre of the disc 40.Although there are advantages in this arrangement, effective separationof dirt may nevertheless be achieved by directing the dirt-laden fluidoff-centre. Moreover, there may be instances for which it is desirableto direct the dirt-laden fluid off-centre. For example, if the centralregion of the disc 40 were perforated, the dirt-laden fluid may bedirected off-centre so as to avoid the region of the disc 40 wheretangential speeds are slowest. As a result, a net gain in separationefficiency may be observed. By way of example, FIG. 14 illustrates anarrangement in which the dirt-laden fluid entering the chamber 36 isdirected off-centre at the disc 40. Similar to the arrangement shown inFIG. 9, the inlet duct 21 is formed integrally with the side wall 31 ofthe container 20, and the bottom wall 32 is attached to the side wall 31by a hinge 33 and catch (not shown). When the bottom wall 32 movesbetween the closed and opened positions, the position of the inlet duct21 remains fixed. This then has the advantage that the container 20 isconvenient to empty without the need to design a hinge and catch capableof withstanding the forces required to manoeuvre the cleaner head 4.Moreover, in contrast to the dirt separator 101 of FIG. 9, the inletduct 21 is straight and thus pressure losses arising from the movementof the dirt-laden fluid through the inlet duct 21 are reduced.

In a more general sense, the dirt-laden fluid may be said to enter thechamber 36 along a flow axis 49. The flow axis 49 then intersects thedisc 40 such that the dirt-laden fluid is directed at the disc 40. Thisthen has the benefit that the dirt-laden fluid impacts the disc 40shortly after entering the chamber 36. The disc 40 then impartstangential forces to the dirt-laden fluid. The fluid is drawn throughthe holes 47 in the disc 40 whilst the dirt, owing to its greaterinertia, moves radially outward and collects in the chamber 36. In thearrangements shown in FIGS. 3, 9, 10 and 11, the flow axis 49 intersectsthe centre of the disc 40, whilst in the arrangement shown in FIG. 14,the flow axis 49 intersects the disc 40 off-centre. Although there areadvantages in having a flow axis 49 that intersects the centre of thedisc 40, effective separation of dirt may nevertheless be achieved byhaving a flow axis 49 that intersects the disc 40 off-centre.

In each of the arrangements described above, the inlet duct 21 has acircular cross-section and thus the inlet 37 has a circular shape.Conceivably, the inlet duct 21 and the inlet 37 may have alternativeshapes. Likewise, the shape of the disc 40 need not be circular.However, since the disc 40 rotates, it is not clear what advantageswould be gained from having a non-circular disc. The perforated andnon-perforated regions 45, 46 of the disc 40 may also have differentshapes. In particular, the non-perforated region 45 need not be circularor located at the centre of the disc 40. For example, where the inletduct 21 is directed off-centre at the disc 40, the non-perforated region45 may take the form of an annulus. In the above discussions, referenceis sometimes made to the diameter of a particular element. Where thatelement has a non-circular shape, the diameter corresponds to themaximal width of the element. For example, if the inlet 37 wererectangular or square in shape, the diameter of the inlet 37 wouldcorrespond to the diagonal of the inlet 37. Alternatively, if the inletwere elliptical in shape, the diameter of the inlet 37 would correspondto the width of the inlet 37 along the major axis.

The disc 40 is formed of a metal, such as stainless steel, which has atleast two advantages over, say, a plastic. First, a relatively thin disc40 having a relatively high stiffness may be achieved. Second, arelatively hard disc 40 may be achieved that is less susceptible todamage from hard or sharp objects that are carried by the fluid or fallonto the disc 40 when the handheld unit 2 is inverted, as shown in FIG.7. Nevertheless, in spite of these advantages, the disc 40 couldconceivably be formed of alternative materials, such as plastic. Indeed,the use of a plastic may have advantages over a metal. For example, byforming the disc 40 of a low-friction plastic, such as polyoxymethylene,the ring of low-friction material (e.g. PTFE) provided around the topwall 30 of the container 20 may be omitted.

In the arrangements described above, the disc assembly 22 comprises adisc 40 directly attached to a shaft of an electric motor 41.Conceivably, the disc 40 may be attached indirectly to the electricmotor, e.g. by means of a gearbox or drive dog. Furthermore, the discassembly 22 may comprise a carrier to which the disc 40 is attached. Byway of example, FIG. 15 illustrates a disc assembly 23 having a carrier70. The carrier 70 may be used to increase the stiffness of the disc 40.As a result, a thinner disc 40 or a disc 40 having a larger diameterand/or a larger total open area may be used. The carrier 70 may also beused to form the seal between the disc assembly 23 and the container 20.In this regard, whilst a contact seal between the disc 40 and the topwall 30 has thus far been described, alternative types of seal mayequally be employed, e.g. labyrinth seal or fluid seal. The carrier 70may also be used to obstruct the central region of a wholly perforateddisc. In the example shown in FIG. 15, the carrier 70 comprises acentral hub 71, connected to a rim 72 by radial spokes 73. Fluid thenmoves through the carrier 70 via the apertures 74 between adjacentspokes 73.

Each of the disc assemblies 22, 23 described above comprises an electricmotor 41 for driving the disc 40. Conceivably, the disc assembly 22, 23may comprise alternative means for driving the disc 40. For example, thedisc 40 may be driven by the vacuum motor 12. This arrangement isparticularly viable with the layout shown in FIG. 1, in which the vacuummotor 12 rotates about an axis that is coincident with the rotationalaxis 48 of the disc 40. Alternatively, the disc assembly 22, 23 maycomprise a turbine powered by the flow of fluid moving through the discassembly 22, 23. A turbine is generally cheaper than an electric motor,but the speed of the turbine, and thus the speed of the disc 40, dependson the flow rate of fluid moving through the turbine. As a result, highseparation efficiencies can be difficult to achieve at low flow rates.Additionally, if dirt were to clog any of the holes 47 in the disc 40,the open area of the disc 40 would decrease, thereby restricting theflow of fluid to the turbine. As a result, the speed of the disc 40would decrease and thus the likelihood of clogging would increase. Arunway effect then arises in which the disc 40 becomes increasinglyslower as it clogs, and the disc 40 becomes increasingly clogged as itslows. Furthermore, if the suction opening in the cleaner head 4 were tobecome momentarily obstructed, the speed of the disc 40 would decreasesignificantly. Dirt may then build up significantly on the disc 40. Whenthe obstruction is subsequently removed, the dirt may restrict the openarea of the disc 40 to such an extent that the turbine is unable todrive the disc 40 at sufficient speed to throw off the dirt. An electricmotor, whilst generally more expensive, has the advantage that the speedof the disc 40 is relatively insensitive to flow rates or fluid speeds.As a result, high separation efficiencies may be achieved at low flowrates and low fluid speeds. Additionally, the disc 40 is less likely toclog with dirt. A further advantage of using an electric motor is thatit requires less electrical power. That is to say that, for a given flowrate and disc speed, the electrical power drawn by the electric motor 41is less than the additional electrical power drawn by the vacuum motor12 in order to drive the turbine.

The dirt separator 10 has thus far been described as forming part of ahandheld unit 2 that may be used as a standalone cleaner or may beattached to a cleaner head 4 via an elongate tube 3 for use as a stickcleaner 1. The provision of a disc assembly in a handheld unit is by nomeans intuitive. Although the provision of a rotating disc within a dirtseparator of a vacuum cleaner is known, there is an existing prejudicethat the dirt separator must include a cyclone chamber to separate thedirt from the fluid. As a result, the overall size of the dirt separatoris relatively large and is unsuitable for use in a handheld unit. Withthe dirt separator described herein, effective separation may beachieved in a relatively compact manner As a result, the dirt separatoris particularly well suited for use in a handheld unit.

The weight of a handheld unit is clearly an important consideration inits design. The inclusion of an electric motor in addition to the vacuummotor is not therefore an obvious design choice. Additionally, where thehandheld unit is battery powered, one might reasonably assume that thepower consumed by the electric motor would shorten the runtime of thevacuum cleaner. However, by using an electric motor to drive the disc,relatively high separation efficiencies may be achieved for a relativelymodest drop in pressure. Consequently, in comparison to a conventionalhandheld cleaner, the same cleaning performance may be achieved using aless powerful vacuum motor. A smaller vacuum motor may therefore be usedthat consumes less electrical power. As a result, a net reduction inweight and/or power consumption may be possible.

Although the dirt separator described herein is particularly well suitedfor use in a handheld vacuum cleaner, it will be appreciated that thedirt separator may equally be used in alternative types of vacuumcleaner, such as an upright, canister or robotic vacuum cleaner.

1. A handheld vacuum cleaner comprising a dirt separator, the dirtseparator comprising: a chamber having an inlet through which dirt-ladenfluid enters the chamber and an outlet through which cleansed fluidexits the chamber; and a disc located at the outlet, the disc beingarranged to rotate about a rotational axis and comprising holes throughwhich the cleansed fluid passes.
 2. The vacuum cleaner of claim 1,wherein the dirt-laden fluid entering the chamber is directed at thedisc.
 3. The vacuum cleaner of claim 2, wherein the dirt-laden fluidentering the chamber is directed at the centre of the disc.
 4. Thevacuum cleaner of claim 1, wherein dirt separated from the dirt-ladenfluid collects at a bottom of the chamber and fills progressively in adirection towards a top of the chamber, the outlet is located at oradjacent the top of the chamber, and the bottom of the chamber is spacedaxially from the top of the chamber.
 5. The vacuum cleaner as claimed ofclaim 1, wherein the chamber extends above and below the disc in adirection parallel to the rotational axis, dirt separated from thedirt-laden fluid collects in a lower portion of the chamber locatedbelow the disc when the vacuum cleaner is used in a first orientation,and dirt collected in the lower portion moves to an upper portion of thechamber located above the disc when the vacuum cleaner is used in asecond orientation.
 6. The vacuum cleaner of claim 1, wherein the inletis defined by an end of an inlet duct, and the chamber surrounds theinlet duct.
 7. The vacuum cleaner of claim 1, wherein the inlet isdefined by an end of an inlet duct that extends linearly within thechamber.
 8. The vacuum cleaner of claim 1, wherein the inlet is definedby an end of an inlet duct that extends through a wall of the chamber,and an opposite end of the inlet duct is attachable to differentattachments of the vacuum cleaner.
 9. The vacuum cleaner of claim 1,wherein the inlet is defined by an end of an inlet duct, a wall of thechamber is moveable between an open position and a closed position, andthe inlet duct is attached to and moveable with the wall.
 10. The vacuumcleaner of claim 1, wherein the disc is formed of a metal.
 11. A stickvacuum cleaner comprising a handheld vacuum cleaner that comprises achamber having an inlet through which dirt-laden fluid enters thechamber and an outlet through which cleansed fluid exits the chamber;and a disc located at the outlet, the disc being arranged to rotateabout a rotational axis and comprising holes through which the cleansedfluid passes, the handheld vacuum cleaner attached to a cleaner head byan elongate tube, the elongate tube extending along an axis parallel tothe rotational axis.
 12. The vacuum cleaner of claim 11, wherein thedirt separator comprises an inlet duct that extends through a wall ofthe chamber, the inlet is defined by a first end of the inlet duct, andthe elongate tube is attached to a second end of the inlet duct.